Order of Kilopi
Just a collection of links, useful for future discussion -- like in 2009 and 2011 when something happens...
NASA Dawn Mission
NASA JPL Dawn Mission Home Page
UCLA Dawn Mission
Planetary Society Space Topics: Dawn: description, blog entries, recent headlines
Nice schematic of voyage:
And, just for decoration, Dawn rising:
Last edited by 01101001; 2007-Sep-28 at 04:27 AM. Reason: added links; refined site names
Order of Kilopi
Rock on, Dawn!
Established Member
Thanks for the links 69. Just curious, is there any potential for an extended mission here, or is the mission end brought on by running out of a key commodity?
Order of Kilopi
I don't think they plan for an extension, but they don't rule anything out. If resources happen to remain after all mission goals are satisfied, well...Originally Posted by Saluki
Dawn Mission FAQ
Wikipedia: Asteroid, less authoritatively:M2: Will there be opportunities to visit other asteroids, either en route to Ceres or as part of an extended mission?
Answer: Unlikely, because there is greater return by spending more of our resources on Vesta and Ceres.
NASA is planning to launch the Dawn Mission in 2007, which will orbit 1 Ceres and 4 Vesta in 2011-2015, with its mission possibly then extended to 2 Pallas.
Order of Kilopi
Yay, Dawn. In the press conference, I think they said...
that 26 hours after launch Dawn would pass the Moon's orbit. That was about 3 hours ago.
Onward and outward.
Newbie
Ok, I'm sure this is a stupid question, but why can't the ship just fly straight out instead of circling around like the planets? I noticed they do the same thing with all their missions.. I just don't understand the reasoning behind it I guess.. Does it have something to do with using the gravitational forces by nature to help increase the speed at which the object travels?Just a collection of links, useful for future discussion -- like in 2009 and 2011 when something happens...
NASA Dawn Mission
NASA JPL Dawn Mission Home Page
UCLA Dawn Mission
Planetary Society Space Topics: Dawn: description, blog entries, recent headlines
Nice schematic of voyage:
And, just for decoration, Dawn rising:
Established Member
Not stupid at all. And it's a multi-part answer.
1. Interplanetary travel takes a lot of time so you have to align your trajectory to end up where your target will be at journey's end, just like a hunter leading a duck in flight or a quarterback pasing the ball to where the receiver will be.
2. Depending on where you are headed you may need to take advantage of gravity assists (which can be used to accelerate or decelerate a spacecraft). You gain speed by aiming to the trailing side of a planet in its orbit - such as when New Horizons passed Jupiter a while back. The gravity of the planet gives a "tug" to the probe. Aim to the leading side and you slow down, or maybe even captured by the planet if that's the intent. It's more complex than that but you have the general idea.
With Dawn it's a complex path because it will visit two bodies and linger a while at each.
Google for Hohmann orbits for more details. Or even search here at BATU.
Established Member
To go like that you must be fast. Really, really, really fast. Burn fuel on beginning to accelerate, later burn fuel on destination to decelerate. In current state of art, this would use absurd quantity of fuel. And we have no engines that can do it.
So we must take it nice and slow. These circley tracks exsists because planets move too, and surpisingly fast. Earth in travel around sun every 4 hours moves distance equal to distance between Moon and Earth.
Order of Kilopi
Though, in this case, with Dawn's ion engines, Hohmann orbits are right out.
UCLA Dawn Mission FAQ:
Question:
Why does it take so long to get to Vesta and then from Vesta to Ceres? The travel time scheduled appears to be significantly longer than would be required by a Hohmann transfer orbit.
Answer:
The reason that Dawn has a longer trip time than might be required by conventional means is that Dawn uses an ion propulsion system which precludes achieving a Hohmann transfer orbit. Hohmann transfer orbits are the most propellant-efficient means of moving between two circular coplanar orbits. Hohmann transfers are certainly not the fastest route between orbits; however, they are used frequently because most missions are tightly constrained in mass, so propellant is a very precious resource.
[...]
Newbie
which would put earth hurling through space at around 50-60k mph? I know that asteroids/comets are generally traveling at 40-60k mph but didnt realize the planets moved so fast as well.. Such huge numbers, quite difficult for many people including myself to grasp.
Order of Kilopi
Wikipedia: Earth
About 66622 mph.Avg. orbital speed: 29.783 km/s
Everything in the neighborhood, to stay in the neighborhood, regardless of mass, has to move like that.
Established Member
If you were on a merry-go-round, and you got off an inner horse and walked to an outer horse, you would take the shortest path - which would be a straight line for you.
But someone sitting in a tree way overhead would see your actual path form a spiral.
How many rotations the spiral made would depend on your walking speed versus the rotational speed of the merry-go-round.
The Earth orbits the sun way faster than the rocket can cross from Earth-horse to Mars-horse.
Established Member
Planetary orbital speeds (in rough terms)
Mercury: 48 km/s
Venus: 35
Earth: 30
Mars: 24
Ceres: 18
Jupiter: 13
Saturn: 10
Uranus: 6.8
Neptune: 5.4
Pluto: 4.7
Eris: 1.2
Established Member
New word from the Dawn Team.
Dawn is 7.90 million kilometers (4.91 million miles) from Earth or almost 21 times farther than the moon.
Established Member
10 planets ? My goodness the IAU would have a field day with this Lord Jub
Established Member
Count again. There are eleven objects listed.
Order of Kilopi
I hadn't realised I hadn't subscribed to this thread. Well now I have.
Order of Kilopi
Fat lot he cares, he's got a royal title.10 planets ? My goodness the IAU would have a field day with this Lord Jub
Established Member
Hey, a dwarf planet is still a planet.
Order of Kilopi
Quite right.Hey, a dwarf planet is still a planet.
Moderator
No it is not
That is what the IAU said on 25 August 2006
Order of Kilopi
To Snow White, they are.
STARGAZING: All I see are the lights of a billion places I'll never go. --Howard Tayler, Schlock Mercenary
Established Member
They have now started posting a "Where is Dawn" page.
It is currently nearly in a straight line with Mars and the Sun and closing in on halfway between Earth and Mars orbits.
Established Member
Dawn is healthy and under power as I post this.
There was evidently a safe mode shut down late in November, but Dawn has been upgraded safely and is accelerating.
Vulcan Administrator
Well, they deliberately rebooted the main computer after upgrading the software, which resulted in a safemode. However, they knew this was going to happen and were prepared for it. (As contrasted with most safemodes, which are a sign that something has happened to the spacecraft outside of anything the spacecraft was designed to handle.)
Everything I need to know I learned through Googling.
Established Member
eh, according to the Journal, the reboot happened spontaneously before the planned reboot.
They used the spontaneous safe mode to initiate the update and reboot Dawn. The cause of the premature safe mode is still under investigation.Around 10:00 pm PST on November 27, the spacecraft's main computer rebooted, just half a day before operators planned to command it, and Dawn entered safe mode. As soon as the Deep Space Network detected the corresponding change in the radio signal and the small night-shift team in mission control realized what had happened, a different plan, known dryly as "anomaly response," was put into action. Some team members were called back in to JPL and spent the entire night investigating this unexpected event; some others were in occasional contact by telephone or Internet. As many team members as possible were not disturbed, so they would be fresh the next day to pick up after the anomaly team's overnight work. (In the same vein, although your correspondent was among those who went to JPL, he opted not to contact you right away; rather, he chose to let you read about it now, under more leisurely circumstances.)
Vulcan Administrator
My bad - what I get for trying to skim a technical discussion.
Everything I need to know I learned through Googling.
Established Member
An update of Dawn's condition:
And closer to Mars than to any other body. Going by the orbital guide that fffizzz posted, they should stop thrusting fairly soon and coast through the ensuing tango with Mars.Dawn Completes Another Month of Thrusting
March 31, 2008
Dawn thrust with its ion propulsion system for most of March, stopping once each week to point its main antenna to Earth. Almost 96% of the month was devoted to thrusting. By the end of March, the spacecraft was farther from Earth than the Sun.
Established Member
No. It shut down in preparation for the long Solar System winter. It started up again in spring.
Established Member
I wonder as a test, the framing camera could be pointed at distant Mars & grab a snap shot?
I hope DAWN gets good views of Phobos & Deimos during the Mars encounter. One other thing that could be attempted would be to get spectra & lightcurves of 4 Vesta soon afterwards, still a long way off, but would give the instruments a great pre-arrival test run.
It is great that this fascinating mission is going so well.
Aother possibility appears to be that after DAWN is finished at 1 Ceres, she could make a close encounter (not orbit) with 2 Pallas in December 2018, dependent on fuel supply & health of the solar panels & instruments.
Andrew Brown.
Last edited by 3488; 2008-Apr-06 at 06:34 PM. Reason: Typo correction.
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